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Chronic Fatigue Syndrome (cont.)

Exams and Tests

There is no single test to diagnose chronic fatigue syndrome. The disease is a diagnosis of exclusion, which means that all other conditions and illnesses that cause the symptoms are ruled out. CFS may be diagnosed based on the following:

Certain signs and symptoms must be present. (People without cognitive dysfunction do not have CFS.)

Some nonspecific laboratory tests, such as blood tests and tests of the immune system, suggest the diagnosis.

Laboratory tests are used to rule out other fatigue-causing diseases. Also, some laboratory abnormalities are seen in CFS and support the diagnosis.

Your doctor may perform the following tests:

Tests to exclude other causes of fatigue: Thyroid, adrenal, and liver function tests are useful to rule out disorders that may cause fatigue. In people with CFS, the results of these tests should be normal.

Blood tests: The most consistent laboratory abnormality in people with chronic fatigue syndrome is an extremely low erythrocyte sedimentation rate (ESR, the measurement of settling red blood cells in anticoagulated [non-clotting] blood). If the ESR is elevated or even in the high-normal range, another diagnosis is likely. If any other abnormalities are found on blood tests, your doctor may rule out CFS and begin testing for another condition.

Antibody tests: Your doctor may order antibody tests to determine whether you have had a prior infection, such as Lyme disease, Chlamydia pneumoniae pneumonia, or Epstein-Barr virus.

Your doctor may perform the following imaging studies:

CT scans or an MRI of the brain is useful to rule out other disorders of the central nervous system (CNS). Results of CT scans and MRI are normal in people with CFS.

Single-photon emission computed tomography and/or positron emission tomography scans show decreased blood flow in areas of the brain (the frontoparietal/temporal region). This decreased blood flow explains the cognitive difficulties (short-term memory problems) in chronic fatigue syndrome.